Visible Implant Alphanumeric tags as an alternative to toe-clipping for marking amphibians – a case study
Geoffrey W. Heard A C , Michael P. Scroggie B and Brian Malone AA Department of Zoology, La Trobe University, Bundoora, Vic. 3086, Australia.
B Arthur Rylah Institute for Environmental Research, PO Box 137, Heidelberg, Vic. 3084, Australia.
C Corresponding author. Email: gwheard@students.latrobe.edu.au
Wildlife Research 35(8) 747-759 https://doi.org/10.1071/WR08060
Submitted: 17 April 2008 Accepted: 29 July 2008 Published: 16 December 2008
Abstract
The removal of toes in unique combinations (‘toe-clipping’) has historically been the most popular technique for individually marking amphibians. However, recent studies have questioned the utility and ethics of this technique, and provided impetus for research on the efficacy of alternative methods. In this study, the efficacy of Visible Implant Alphanumeric (VIA) tags for marking juvenile growling grass frogs (Litoria raniformis) was assessed with reference to the fundamental assumptions of the mark–recapture approach. Three questions were investigated: (1) What is the probability of tag loss? (2) What is the probability of tag misidentification, and does it vary between frogs or observers, or with observer experience? and (3) To what extent does tagging influence survival or growth? Laboratory and field trials demonstrated that the probability of tag loss for juvenile L. raniformis was ~0.07 (95% CI: 0.03–0.13) when tags where implanted on the dorsolateral region of the thorax, eight times lower than that estimated for tags implanted on the thigh (mean 0.59; 95% CI: 0.29–0.86). Tags were rarely misidentified by naïve observers (mean probability of tag misidentification <0.01), but tag read accuracy varied amongst observers. In the laboratory, tagging did not adversely influence survival or growth of L. raniformis during the 12-week study period. Given that modification of the techniques used here may eliminate tag loss, and that variation in tag read accuracy between observers may be easily avoided, it is concluded that VIA tags represent a promising alternative to toe-clipping for marking L. raniformis and other amphibians.
Acknowledgements
We thank Nick Clemann, Graeme Gillespie, Andrew Hamer, David Hunter and Peter Robertson for discussion of marking techniques for anurans. We are particularly indebted to Arthur Buchan for provision of information on the use and implantation of VIA tags whilst planning this project. Gerry Marantelli and his staff at the Amphibian Research Centre allowed tagging of juvenile L. raniformis in their collection during the pilot study. We are indebted to volunteers who contributed to the tag read accuracy and field trials. Tanja Beer, Rob Heard, Wendy Moore, Prue Simmons, Jeremy Tscharke and Rob Valentic are particularly thanked for their assistance with the latter. For access to private property we acknowledge Richard and Margaret Lloyd, John and Margaret Glide, Austral Bricks Pty Ltd, Boral Pty Ltd, Hanson Pty Ltd and Shell Pty Ltd. Parks Victoria granted access to the Craigieburn Grasslands. Michael McCarthy discussed the use of Bayesian statistics, and Nick Clemann, Andrew Gormley and Kirsten Parris kindly reviewed an earlier draft of this manuscript. GH was supported by a David Myer Postgraduate Scholarship and Dean’s Top-Up Award (La Trobe University). The project was funded by grants from La Trobe University, the Growling Grass Frog Trust Fund (composed of the Victorian Department of Sustainability and Environment, Australian Gas Limited, and Friends of Merri Creek), and the Victorian Department of Sustainability and Environment. This study was undertaken pursuant to the provisions of the Wildlife Act 1975, in accordance with the conditions of research permit no. 10003005. It was approved by the La Trobe University Animal Ethics Committee (approval number AEC04/24(L)/V4).
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